70 A HALF-HOUR WITH THE 



first plate. "With these tliey seem to have the 

 power of moving, as well as of taking up the 

 matters by which they are nourished. The shells 

 of these creatures are not so small but they may 

 be seen with the naked eye, and they need only a 

 low power to observe all their structure. They are 

 found at great depths in the ocean, and have been 

 brought up by the dredge from the deepest parts of 

 the Atlantic. They are very abundant in some 

 rocks, especially in the chalk : they may be ob- 

 tained from the latter substance by rubbing a piece 

 of chalk with a brush in water. The water must 

 be first decanted from the coarser particles of chalk, 

 and in subsequent deposits the foraminifera will be 

 found. They may be obtained from dry sand in 

 which they are contained, by throwing the sand 

 into water, when tlie sand will sink and the 

 foraminifera will swim on the surface, and may be 

 skimmed oS. They are best examined as opaque 

 objects. 



The family of polyps will next command atten- 

 tion. One of the most simple forms of this family 

 is found in ponds and rivers, and is called the 

 fresh- water polyp or hydra. It is figured at 146, 

 plate 5. It may be easily observed, adhering to 

 plants, with the naked eye, and needs only a low 

 power with transmitted light to observe it accu- 

 rately. Its body is cup-shaped, surmounted with 

 eight long tentacles, which it has the power of re- 

 tracting. It produces young ones by the process of 

 budding, and the buds may be often seen protrud- 

 ing from the side of their parents. It is very 

 tenacious of life, and may be cut into several pieces, 

 and each part will grow into a new hydra. These, 

 with many other polyps and the jelly-fish, have their 

 flesh filled with little hair-like bodies, which, from 

 their property of stinging in some species, havo 



